In semiconductor processing, a large number of semiconductor substrates are processed in a semiconductor facility. For example, integrated circuit devices are fabricated on circular single crystal silicon substrates. Solar cells are typically fabricated in square or rectangular substrates, either single crystal silicon or polycrystalline silicon. The substrates are stored in carriers, which are designed to hold each substrate separately without touching each other.
During single substrate processing, individual substrates are brought from the carriers to a processing chamber, where each substrate is processed separately. During batch processing, such as a wet etch process, multiple substrates are transferred to a process carrier, which supports the substrates with adequate separate between the substrates to enable uniform processing of all substrates within the carrier. The carrier is then submerged in a tank filled with chemical liquid, which can etch all substrates at a same time.
FIGS. 1A-1C illustrate an exemplary prior art process carrier for a wet processing. In FIG. 1A, a carrier 100 is shown, supporting substrates 110. The carrier 100 comprises two end plates 120, together with a number of rods 130. The rods are spaced as to allow the substrates to be positioned between the rods. The carrier 110 can comprise side rods for support the sides of the substrates, and bottom rods for support the substrate bottom. Option top rods can be included, for example, to prevent dropping of the substrates during movements. The rods 130 can comprise teeth 135, which can separate the substrates.
FIG. 1B shows a detailed of a portion of a rod 130 with teeth 135. The teeth comprise a cylindrical shape, disposed in a horizontal direction. The separation of the teeth is large enough to accommodate the substrate 110. During liquid processing, droplets 140 can be adhered to the carrier surfaces, such as on the surfaces of the tooth 135A (FIG. 1C). When wet processing is completed, the carrier is removed from the liquid tank. The droplets 140 can migrate along the surface of the teeth, and potentially dropping on the substrate 110, forming contaminated spot 145.